"Unscrupulous people using relatively inexpensive software and devices-actually legal for recalibrating faulty odometers-can reprogram digital odometers," explains Larry Gamache of Carfax. "The value of a car can drop by as much as $5,000 if odometer fraud is detected."

Fortunately, there are ways to protect yourself from odometer fraud:

• Ask to see the vehicle's title and compare mileage on it with the vehicle's odometer.

• Compare the mileage on the odometer with the mileage indicated on the vehicle's maintenance inspection records. Also, search for oil-change and maintenance stickers on windows or door frames, in the glove box and under the hood.

• Request a Carfax Vehicle History Report to check for odometer discrepancies in the vehicle's history. If the seller doesn't have a report, you can use the car's VIN number to order one online.

• Check that the numbers on the odometer gauge are aligned correctly. If they're crooked, contain gaps or jiggle when you bang on the dash with your hand, you may want to walk away.

• Examine the tires. If the odometer shows 20,000 or fewer miles, the car should have the original tires.

• Look at the wear and tear on the vehicle-especially the gas, brake and clutch pedals-to be sure it seems consistent with and appropriate for the number of miles indicated on the odometer.

For more information, visit www.carfax.com.